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Am J Physiol Heart Circ Physiol 292: H1533-H1540, 2007. First published November 17, 2006; doi:10.1152/ajpheart.00837.2006 Free Article
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Wave intensity analysis of left atrial mechanics and energetics in anesthetized dogs

Tracy N. Hobson, Jacqueline A. Flewitt, Israel Belenkie, and John V. Tyberg

Departments of Cardiac Sciences and Physiology/Biophysics, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada

Submitted 3 August 2006 ; accepted in final form 9 November 2006

The left atrium (LA) acts as a booster pump during late diastole, generating the Doppler transmitral A wave and contributing incrementally to left ventricular (LV) filling. However, after volume loading and in certain disease states, LA contraction fills the LV less effectively, and retrograde flow (i.e., the Doppler Ar wave) into the pulmonary veins increases. The purpose of this study was to provide an energetic analysis of LA contraction to clarify the mechanisms responsible for changes in forward and backward flow. Wave intensity analysis was performed at the mitral valve and a pulmonary vein orifice. As operative LV stiffness increased with progressive volume loading, the reflection coefficient (i.e., energy of reflected wave/energy of incident wave) also increased. This reflected wave decelerated the forward movement of blood through the mitral valve and was transmitted through the LA, accelerating retrograde blood flow in the pulmonary veins. Although total LA work increased with volume loading, the forward hydraulic work decreased and backward hydraulic work increased. Thus wave reflection due to increased LV stiffness accounts for the decrease in the A wave and the increase in the Ar wave measured by Doppler.

hemodynamics; left atrium; A wave; Ar wave; Doppler echocardiography


Address for reprint requests and other correspondence: J. V. Tyberg, Health Sciences Centre, Univ. of Calgary, 3330 Hospital Drive N.W., Calgary, Alberta, Canada T2N 4N1 (e-mail: jtyberg{at}ucalgary.ca)






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